Range-finder.



No. 801,578. PATENTED 00T. 10, 1905. B. A. FISKE.

RANGE FINDER. APPLICATION FILED NOV. 251902.

PATENTED 00T. 10, 1905.

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Witnesses No. 801,578. PATENTED OCT. 10, 1905.

B.. A. FISKE.

RANGE FINDER.

APPLIUATION FILED Nov. z5 1902.

a SHEETS-SHEET a.

IIIIIIPI|I|||I|| l l l 20 30 .4o 5o Z u ou 0M5 oc: D 0 Oka a M V om "I H Inventor UNITED sTATEs PATENT oEEroE.

BRADLEY A. FISKE, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

`RANGE-'FINDER- Specification of Letters Patent.

Patented Oct. 10, 1905.'

To all whom, it may concern:

Be it known that I, BRADLEY A. FrsKE, a citizen of the United States, residing in the borough of Manhattan, city of New York, State of New York, have invented a certain new and useful Improvement in Range-Finders, of which the following is a description.

My invention relates to improvements in range-finders adapted particularly for nautical use and of the type employing a known horizontal base-line with respect to which .the distance of the target is calculated trigonometrically. My object is to provide4 a range-iinder of this character involving extremely simple apparatus, which is not liable to mechanical derangement, by which the operation of determining the range of the target can be performed quickly and expeditiously, and wherein the calculations are more exact and certain than is the case with purely automatic range-finders as heretofore invented and patented by me.

In carrying my invention into effect on a inan-o'f-war, for example, I employ two telescopes located near the extremities of the vessel and separated by a definite distance to constitute a known base-line. These telescopes coperate with scales in order th at the angle between them and the base-line can be accurately determined. The observers at the two telescopes are connected telephonieally with a reader who may be located in the chart-room or other convenient position. The telescopes are directed toward the'target-an enemys war-ship or a hostile fort,for example-and the angle of each telescope to the base-line is then communicated telephonically to the reader. By means of a suitable chart of angles and a properly-graduated rule, with which the reader is supplied, the distance of the target can be immediately determined. The so-called chart of angles and its cooperating ruler constitute very simple and convenient means by which the trigonometrical problem can be solved, and they form a very important feature of my invention.

In order that the invention may be better understood, attention is directed to the accompanying drawings, forming part of this speciiication, and in which- Figure 1 is a diagrammatic view showing the two telescopes at the ends of a known base-line with their coperating scales and the distant target; Fig. 2, a view illustrating the ruler for cooperation with the chart of angles, and Figs. 3 and 3at views of the socalled chart of angles.

Referring to Fig. 1, A B represent a known base-line, and T the target. 1 2 are telescopes mounted at the ends of the base-line A B and cooperating with scales 3 3. These scales are graduated in degrees and minutes of angle from lthe baseline. Thus ifl either vtelescope is directed perpendicular to the base-line a pointer carried thereby indicates ninety degrees on the corresponding scale. If directed at an angle of forty-iive degrees from the base-line, its pointer indicates fortyf five degrees, &c. The two operators at the telescopes 1 and 2 are, as stated, connected telephonically with a reader located in the chart-house or elsewhere. When it is desired to determine the range of the distant target T, both telescopes are directed thereon and at a given signal a reading of the angle of each telescope is taken-l These readings are communicated to the reader by the telephone. Knowing the length of the base-line A B between the pivots of the two telescopes and knowing also the an ies, it remains simply to solve the triangle ormed by the-baseline and the lines running from the ends of the base-line to the target. Thus by trigonometry:

ABsin.ABT AT- sin.ATB and ABsin.BAT BT sin.ATB Therefore AT-l-BT:

AB sin.ABT-lsin.BAT.

sin.ATB 2 By my invention I solve this equation and iind the mean of the two distances A T and B T by means of the so-called chart of angles illustrated in Figs. 3 and 3a.

It will be noticed that the middle horizontal line marked 90" is divided into iive equal main parts and that each one of these parts is divided intov thirty smaller parts. Each one of the ve main parts represents an angle of one degree, and each one of the smaller divisions represents, therefore, an

IOO

angle of two minutes, All the other horizontal lines are similarly divided; but it will be noted that the divisions are proportionately longer in those lines that are farther away from the middle horizontal line. words, divisions on the line marked 45. are longer than those on the line marked and these in turn are longer than those on the line marked 90o. The length of each one oi these large divisions on anyparticular line may be thus' calculated: Take, for example, the first main division on the forty-ivedegree line. The length oi' this division is equal to the length of the irst division on the ninety-degree line divided by the sin. of forty-five degrees plus the sin.. of fortysix degrees divided by two. The length of the iiist division on the iorty-six-degree line immediately below it is equal to that of the 'iirst division on the ninety degree line divided by the sin. of forty-six degrees plus the sin. of forty-seven degrees divided bytwo; Similarly, the length of the iirst division on the line marked 1200, for example, is equal to that of the first division on the ninety-degree line divided by the sin. of onehundred and twenty degrees plus the sin. of one hundred and twenty-one degrees divided by two. Take now the second division on any horizontal line. This represents also an angle of one degree between two angles but each angle is one degree larger than the aiigles limiting the space to the left oi it'-that is, the second space on the forty-iive-degree line represents from forty-six to forty-seven degrees, while the second space on the onehundred-and-twenty-degree line represents from one hundred and 'twenty-one to one hundred and twenty-two degrees, and the length in each case is equal to the length of the first division on the ninety-degree line multiplied by the mean of the sines of these two angles-that is to say, the length of the second division on the forty-five-degree line is equal to the length of the first division on the ninety-degree line multiplied by the sin. of forty-six degrees plus the sin, of forty-seven degrees divided by two, &c. In the same way the third'division on any line represents an angle of one degree between two angles; but each angle is one degree greater than the division limiting the space on the leftthat is to p say, the third division on the forty-iive-degree line represents the space between forty-seven and'forty-eight degrees, and its length is equal to the vFirst division on the ninety-degree line multiplied by the sin, of fortyseven degrees plus the sin. of forty-eight degrees divided by two, &c.

In Fig. 2 I illustrate a ruler for use in connection with this chart of angles and on which the iirst graduation is iniinity, the other graduations being thus determined: Suppose the base-line to be, say, seventy yards. Now if the target wei'e at such a dis- In other B A 'regagner sin. fe-

is so near to unity that it may be neglected,

then the distance would be AB I 7o sin.ATB .01745 (approximately.) Ii, now, the distance on this rule from infinity to four thousand (representing yards) equals the distance on the ninety-degree line of one division, then it is plain that if we put the rule on the ninetydegree line with the infinity-mark at the extreme left the indication of four thousand yards will register with the lirst heavy line. In other words, suppose the angle A.B T were ninety degrees and the anglerB A T were eighty-nine degrees. Then, the rule being placed on the ninety-degree line so that the infinity-niark registers with ninety degrees, the distance on the ruler representing four thousand yards will correspond to an angle of one degreei. e., the four-thousand mark will register with the main division at the right, Similarly, if the angle A T B were two degrees then the solution of the equation would make the distance A T one-half of four thousand, or two thousand, (approximately.) Therefore il the two thousand mark is placed on the rule at twice the distance from the infinity-mark of the fourthousand niark and if the angle A B T were, say, ninety degrees and the angle B A T were eighty-eight degrees then if the ruler is placed on the ninety-degree line with the infinity-mark opposite ninety degrees the distance between the infinity-mark and the indication of two thousand yards will correspond to an angle of two degrees-i. e., the range or' two thousand yards will register with the second main line at the right.

We see that this method of graduating the ruler is Isimplya reciprocal method in which the distance from the infinity or ystarting mark to any graduation multiplied by that graduation is a constant. Therefore, con= sidering for the moment the case in which the target is so nearly perpendicular to the base-line that the expression v sin. ABT-l-sin. BAT f3 might be neglected, it is evident that if we simply graduate the rule according to this plan and then place the infinity-mark along the ninety-degree line in such a way that it comes opposite the iirst angle the mark on IOO IIO

the rule opposite the second angle will al- Ways be the range corresponding to those angles and the base-line. For instance, suppose the first angle is ninety degrees ten minutes and the second angle ninety-one degrees twenty minutes. The distance is found by registering the infinity-mark on the ruler with the graduation on the ninety-degree line representing 90o 10 and noting the range-mark on the ruler registering with the mark corresponding to ninety-one degrees twenty minutes. We thus see, considering the theory on which this chart is made, that no matter what the angles are it is only necessary to place the ruler on the proper degree-line in such a way that the infinity-mark registers with the first angle andto then note the graduation on the ruler corresponding with the second angle. Thus, if the first angle were forty-five degrees ten minutes and the second angle forty-six degrees thirty minutes it is only necessary to register the infinity-mark with the graduation 45 10 and to note the range-mark on the rule registering with the graduation corresponding to forty-six degrees thirty minutes.

It will be understood, of course, that instead of employing a chart, as explained, a long tape might be used marked with the several degrees from forty-iive degrees to one hundred and thirty-five degrees (assuming the capacity of the apparatus to be-ineluded Within these extremes) and by observing on the ruler the range-mark included between the noted angles. Such a tape would, however7 be very long and bulky and would therefore be objectionable. For this reason a chart is used.

Since the degree-marks on the forty-fivedegree line are, as stated, longer than the corresponding degree-marks on the ninety-de- 'gree line, it is not possible with a chart of a convenient rectangular form to include all gle is forty-six degrees and the second angle forty-seven degrees, the ruler may be used on the forty-ive-degree line with the infinitymark on the rst main division representing fortysix degrees and the range observed at the next main degree-line, or the rule may be placed on the forty-six-degree line with the iniinityemark at the extreme left and the reading on the scale be observed at the next main degree-line at the right.

Having now described my invention, what I claim as new therein, and desire to secure by Letters Patent, is as follows:

1. A chart for use with range-finders, having a plurality of parallel division-lines with curved crossing lines dividing the divisionlines into spaces each representative of a certain angular difference between two angles divided by the mean of the sines of those angles, substantially as set forth.

2. A chart for use with range-finders, having a plurality of parallel division-lines with curved crossing lines dividing the divisionlines into spaces each representative of a certain angular difference between two angles divided by the mean of the sines of those angles, and a ruler having range-marks thereon cooperating with said ch art, substantially as set forth.

This specification signed and witnessed this 25th day of October, 1902. f

Y BRADLEY A. FISKE.

Witnesses:

FRANK L. DYER, JNO. RoBT. TAYLOR. 

